package C;

import java.util.Scanner;

public class C15My {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] arr = sc.nextLine().split(" ");
        double sum = 0;
        for (String s:arr){
            sum+=s.length();
        }
        System.out.println(String.format("%.2f",sum/ arr.length).toString());
    }
}
